(1) Field of the Invention
This invention relates to an aluminum-permanganate battery and more particularly to an aluminum-permanganate battery wherein the permanganate is in solution.
(2) Description of the Prior Art
Presently, a high power density primary battery based on aluminum and silver oxide alkaline half cells provides sufficient energy for vehicle propulsion. Major advantages of this electrochemical system are the high theoretical energy density, in excess of 900 Watts-hours/Kilogram (W-hrs/kg), and the extraordinary current and power densities, in excess of 1 ampere/cm.sup.2 and 1 watt/cm.sup.2 which respectively are readily achieved. The high current densities are indicative of facile electron transfer in both the anodic and the cathodic redox couples. However, a major disadvantage of the alkaline aluminum silver oxide primary battery is the significant cost of the cathode. Many attempts have been made to address the issue of cost. As an example, Anderson, U.S. Pat. No. 3,953,239, discloses a primary battery comprising aluminum and silver oxide in alkaline electrolyte for the generation of power. Hunter, U.S. Pat. No. 5,004,56; Tarcy, U.S. Pat. No. 4,950,650; Moden, U.S. Pat. Nos. 4,107,406, and 4,150,204; Pryor, U.S. Pat. No. 3,189,486; and Bohnstedt, GB No. 2020478 disclose solid and solution phase aluminum anode modifications, and do not indicate coupling such an anode with a permanganate cathode for electrochemical energy storage. Aqueous permanganate is a strong oxidant which readily attacks aluminum and therefore had not been previously considered for electrochemical storage in such a media.
Even anodes less electronegative than aluminum will also react when in contact with solution phase permanganate. This necessity and requirement to prevent solution phase permanganate from reaching the anode was recognized in the (zinc) alkaline dry cell of U.S. Pat. Nos. 3,620,848 and 3,799,959. In particular, Epstein et al use an insoluble permanganate to physically separate and prevent permanganate interaction with the anode. It has been proposed in U.S. Pat. Nos. 3,620,848 and 3,7999,959 to provide alkaline dry cells wherein an insoluble alkyl ammonium permanganate salt is used as a cathode. The low conductivity, high molecular weight and organic nature of these salts result in cathode limitations. Even with graphite powder added to the insoluble permanganates, conductivity remains low. The cathode will therefore only support low current densities. The high molecular weight of the organic cation results in diminished theoretical faradic capacity and energy density.
It would thus be desirable to provide a battery capable of producing high current densities and high charge capacity. In addition, it would be desirable to provide such a battery formed of relatively inexpensive materials for forming the cathode, anode and electrolyte.
It is an object of subject invention to have a battery which is formed of relatively inexpensive materials for the cathode, anode and electrolyte thereof.
Another object of the invention is to have a battery which is capable of producing high current densities.
Still another object of subject invention is to provide a battery which has high charge capacity.